Rotary valves are commonly used in devices for controlling fluid flow. A typical type of valve, for example used in laboratory equipment of moderate sizes such as a liquid chromatography system (LCS), is a rotary selection valve employed to select an appropriate fluid path from a number of paths and thus to redirect fluid from one fluid path to another fluid path.
Generally, a rotary valve has a stationary body, herein called a stator, which co-operates with a rotating body, herein called a rotor.
In commercially available LCS rotary valves, the stator is provided with a number of inlet and outlet ports. The ports are in fluid communication with a corresponding set of orifices on an inner stator face, via bores in the stator. The inner stator face is an inner surface of the stator that is in generally fluid tight abutment with an inner rotor face of the rotor. The rotor is typically formed as a disc and the inner rotor face is pressed against the inner stator face in rotating co-operation. The inner rotor face is provided with one or more grooves which interconnect different stator orifices depending on the rotary position of the rotor with respect to the stator.
Rotary valves can be designed to withstand high pressures (such as pressures above 30 MPa). They can be made from a range of materials, such as stainless steel, high performance polymeric materials and ceramics.
The number of inlets/outlets as well as the design of grooves in the rotator or the stator reflects the intended use of a specific rotary valve.
A common type of multi-purpose valve has one inlet port (typically placed in the rotary axis of the valve) and a number of outlet ports that are placed around the inlet port. The rotor has a single, radially extending groove that has one end in the rotary axis, thereby always in fluid communication with the inlet, while the other end can be in fluid communication with any one of the outlets depending on the angular position of the rotor with respect to the stator. Such a valve is useful to direct a flow from the inlet to any of the outlets, one at a time. Other arrangements of fluid paths are known also.
Whilst these valves function very well, small amounts of leakage are possible between the abutting rotor and stator faces, which manifests itself as growths of bacteria and other microorganisms, usually around the orifices on the stator where the leakage has taken place. This in turn leads to contamination in the fluid paths as the rotor moves between selected angular positions. For highly sensitive laboratory equipment, this contamination is not acceptable, and so the valve has to be dismantled and cleaned regularly, which takes time and renders the equipment inoperable during cleaning.
One attempt to address the above issue is described in, as yet unpublished, application PCT/EP2013/058752, which provides improved rotary selection valve that requires less cleaning and is thus more convenient to use. That invention consists in a rotary selection valve, the valve comprising a stator and a rotor, said stator and rotor each having complementary abutment surfaces for allowing generally fluid tight relative rotation between the stator and the rotor about a rotational axis, said stator or rotor comprising at least one connection port in fluid communication with an associated orifice at said stator or rotor abutment surface, that invention being characterised in that said stator and/or said rotor further comprises a fluid recess extending radially beyond said associated orifice or orifices and open to the complementary abutment surfaces.
Thereby, the inventor observed that arrangement allows easier cleaning or sanitisation of the valve, because bacteria or other microorganisms cannot pass radially beyond the fluid recesses described above. The valve can be cleaned by automated means and need not be dismantled so frequently.
However the same inventor has realised that an even better system is possible which cleans the whole internal valve assembly including the complementary abutment faces mentioned above, which system can be readily automated. Embodiments of the present invention address this realisation.
The invention provides rotary valve according to claim 1 having preferred features defined by claims dependent on claim 1. The invention provides also a method as defined by claim 9 having preferred features define in subsequent claims.